Accused school killer Nikolas Cruz is a "remorseful" and "broken child" whose life came apart after the devastating loss of his mother in November, his attorneys say.

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Cruz, 19, remains on suicide watch at the Broward County jail after being ordered held without bond Thursday on 17 counts of premeditated murder after the shooting Wednesday at Marjory Stoneman Douglas High School in Parkland.

Wearing orange jail scrubs and shackled at the waist and ankles, he looked down and said two words – “Yes, ma’am” — when Circuit Judge Kim Mollica asked him if he understood the charges.

Cruz had a fascination with guns, was avoided by students at the high school before he was expelled and once trained with a white supremacist group. He also might have sent a Youtube comment in September saying: "I'm going to be a professional school shooter.''

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But his attorneys, in an emotional news conference, tried to paint a sympathetic portrait of a sad teenager who has expressed remorse for the shootings, which culminated a life that spiraled out of control in recent months.

“He is a deeply troubled child who has endured significant loss. He fell between the cracks,’’ said Gordon Weekes, executive assistant public defender.

“He is also saddened by the loss of those family members, by the loss of those children. He has expressed that.”

Cruz and his biological brother Zachary were adopted at birth by an older couple. His father died 13 years ago and his mother Lynda died from pneumonia on Nov. 1 after Cruz had tried to persuade her to seek medical help.

“He encouraged her to go to the hospital to seek treatment. That didn’t work out. That is a significant bit of trauma this young man endured in a very short period of time,” Weekes said.

Assistant public defender Melisa McNeill said Cruz has suffered from mental illness throughout his life and that it’s possible he is autistic.

“He is a broken human being. He is a broken child,’’ she said.

Right after his mother died, Cruz lived for a few weeks with a family friend at the Lantana Cascades Mobile Home Park west of Lantana. About Thanksgiving, he was taken in by the Snead family in Pompano Beach, where he had his own room.

WATCH: Suspected Florida High School Shooter Nikolas Cruz Appears In Court

"The family took him in. They knew his mom had died. They got him a job at Dollar Tree. And they helped him continue his education. They're totally shocked,'' said attorney Jim Lewis, who represents the Sneads.

The Sneads have a 17-year-old son who is a junior at the high school and was there during the shooting, Lewis said.

“They didn’t have any clues,” Lewis said. “They didn’t see anything in this kid, that he was a danger or that he harbored any ill feelings toward the high school.”

In September, the FBI was warned about an eerie comment on a Youtube channel from a user named Nikolas Cruz: “I’m going to be a professional school shooter.’’

Robert Lasky, special agent in charge of the FBI's Miami office, confirmed Thursday that the agency had looked into the "professional shooter" comment but could not uncover any details from the account.

“No other information was included in the comment, which would indicate a time, location, or true identity of the person who made the comment,” Lasky told reporters. “The FBI conducted database reviews, checks, but was unable to further identify the person who made the comment.”

On Wednesday, hours after the shooting, Buzzfeed reported that a video blogger from Mississippi saw the comment from a user named Nikolas Cruz and informed the FBI.

The Nikolas Cruz YouTube account remained active until Wednesday evening. It has since been deleted.

Ben Bennight, the blogger who reported the Cruz comment, said he alerted the FBI in September and told agents from the Mississippi field office that he didn’t know anything about the user.

That was the last contact he had with the FBI until Wednesday, he told CNN.

"I saw the story kind of go across my newsfeed, but I didn't pay a whole lot of attention to it," he recalled Thursday. "But when the FBI said it was the same name, the first thing that went through my mind was, 'Wow, I hope you were at least watching this guy that I alerted you to months ago.'"

Also Thursday, the Anti Defamation League announced that it had been told by Republic for Florida, a white supremacist group, that Cruz had trained with the group.

ROF member Jordan Jereb, who is based in Tallahassee, told the ADL that Cruz had been “brought up” by a member. “Jereb added that Cruz had participated in one or more ROF training exercises in the Tallahassee area, carpooling with other ROF members from South Florida,’’ according to an ADL blog post.

Jereb said that ROF had not ordered or wanted Cruz to do anything like the school shooting, the ADL said.

Later on social media, Jereb said there been a misunderstanding.

"There was a legit misunderstanding because we have MULTIPLE people named Nicholas in ROF," he said in a profanity-laced post on Twitter and on a website called Gab.

Cruz was known among Douglas students as “a weird kid. No one really talked to him,’’ said Dylan O’Neill, 15, a sophomore.

Cruz was dropped off at the school just after 2 p.m. by an Uber driver, according to sheriff's report.

A witness who recognized Cruz as “a former troubled student” saw him get out of a small “goldish colored” vehicle wearing black pants, a black hat and a maroon shirt – later identified as having school logos on it.

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He also carried a duffel bag and wore a black backpack.

The witness radioed a co-worker that “Cruz was walking purposefully” toward a building at the school. Less than a minute later, about 2:23 p.m., gunshots rang out.

Cruz pulled the fire alarm to lure students out of the building, according to Sen. Bill Nelson.

Cruz legally bought the AR-15 used in the mass shooting, according to the sheriff’s report. The report indicates he also confessed to the shooting.

“In a post Miranda statement, Cruz stated that he was the gunman who entered the school campus armed with a AR-15 and began shooting students that he saw in the hallways and on the school grounds.’’

On Thursday, Cruz appeared on closed circuit video in a courtroom that was cleared of all other inmates. Cruz, who is slight and skinny, looked down the entire time he was before the judge.

“You are charged with some very serious crimes,” Mollica told him.

After the hearing, Weekes said Cruz is remorseful but also mentally disturbed.

“He is deeply sad. He is dealing with the shock of all of this from this point on. He recognizes the loss that this community faces and more important the loss of those family members,’’ Weekes said.

Weekes was overcome by emotion several times as he tried to speak in Cruz’s defense.

“The child is deeply troubled and he has endured significant trauma that stems from the loss of his mother,” he said.

“There are losses on all sides.”