Two men were killed in separate shootings that happened within one hour in Gwinnett County on Sunday morning.

Police said a 21-year-old died after being shot in the torso in a Snellville neighborhood about 2 a.m. Then, shortly after 2:50 a.m., police responded to a triple shooting at a shopping center in Norcross and found one victim dead at the scene, Gwinnett police said in a statement.

In the first incident, officers responded to a home on Forrest Bend Lane and found the victim inside the residence. He was identified by police as Pascual Jose Sarabia of Norcross.

Later, an off-duty Gwinnett officer working security at a karaoke restaurant along Britt Road went to investigate after hearing shots ring out nearby, officials said.

The officer drove through the shopping center and located three victims, Gwinnett police said. One man was dead at the scene, and two others were wounded. The man killed was later identified as 22-year-old Dennis Guifarro of McDonough, according to Gwinnett police.

The other two victims, 24-year-old Federico Allen Brown and 18-year-old Adan Guifarro-Buendilla, also from McDonough, were treated at a hospital and released.

Investigators have not determined a motive in either shooting or announced any arrests. Both cases remain under investigation, and anyone with information is asked to call Gwinnett homicide detectives at 770-513-5300.

Tipsters can remain anonymous, and be eligible for cash rewards, by contacting Crime Stoppers at 404-577-8477, texting information to 274637 or visiting the Crime Stoppers website.