At least 10 people were shot, 4 fatally in a mass casualty shooting after someone opened fire at a family gathering in Fresno, California Sunday night, police said.

A suspect or multiple suspects snuck into the gathering of family and friends in a backyard on the 5300 block of East Lamona Avenue near Caesar Avenue in southeast Fresno while they were watching a football match and started shooting, Police Lt. Bill Dooley told NBC affiliate KSEE. At least 35 people were present at the party when the suspect approached and opened fire.

Officers responded to the scene around 8 p.m. after they received multiple calls Sunday. At least 10 people were shot and three men were found dead on the scene. One man died after he was taken to the Community Regional Medical Center, a local hospital, Fresno Police Deputy Chief Michael Reid said.

All four men were Asian and aged between 25-30.

Additionally, 5 other victims were taken to the hospital with non-critical gunshot wounds and one other patient was being treated for graze wound, Reid added.

“What we do know is that this was a gathering, a family and friend gathering in the backyard,” Dooley told reporters. “Everyone was watching football this evening when unknown suspects approached the residence, snuck into the backyard and opened fire.”

"My heart goes out to the families that are victims of this senseless violence," Reid said. "We are going to do everything we can to find out who the perpetrators are and bring them to justice"

The suspect or suspects are still at large and the motive behind the attack still remains unknown. However, Dooley said that the police are investigating the matter, talking to witnesses and checking for anyone with surveillance cameras in the area. The police also declined to comment on the getaway vehicle.

crime scene
Crime scene. BRENDAN SMIALOWSKI/AFP/Getty Images