Authorities have identified the victim and suspect involved in a homicide in the Midway District over the weekend that led to a six-hour standoff in North Park.

San Diego police say 27-year-old Alexander Mazin was shot to death behind a 24-Hour Fitness on Midway Drive just before 11 a.m. Sunday. The lone suspect in the shooting, who remains out of custody Wednesday, was identified as Ernesto Castallenos Martinez.

The San Diego Police Department (SDPD) responded to the scene to find Mazin laying on the ground, suffering from bullet wounds to his upper torso. Mazin was pronounced dead at the scene shortly after.

Witness Monica Stepanof was at the gym when the victim was shot.

“I grabbed some towels at the front desk and ran to the back where I found the gentleman slumped over by his truck with a gunshot wound to his neck and his back and blood everywhere," she said.

At around 12 p.m., an SDPD SWAT team surrounded an apartment complex near the intersection of Upas and Ray streets in North Park where investigators believed Martinez was holed up.

TRAFFIC ADVISORY: Our SWAT Team has been called out regarding a barricaded suspect in Mid City. Please avoid the areas of 3000 Upas and 3000 Ray Street. More info to follow. pic.twitter.com/kJvB0per4v — San Diego Police Department (@SanDiegoPD) February 25, 2018

Police attempted to make contact with Martinez for more than five hours before executing a search warrant at the residence. SWAT units did not find Martinez inside and authorities are still investigating his whereabouts.

SDPD detectives said Sunday that the suspect was in his apartment at some point after the shooting, but they did not know how or when he left.

The department is asking anyone with information regarding Martinez' location to contact call the Homicide Unit at (619) 531-2293 or Crime Stoppers at (888) 580-8477.

Several blocks of Upas and Ray streets were closed off for hours due to the heavy police presence. Residents were not able to enter their homes and several businesses were closed.