A security guard was arrested after admitting to fatally stabbing a 37-year-old man in Santa Monica, police said Tuesday.

Officers with the Santa Monica Police Department's Homeless Liaison Program responded to the 1100 block of Sixth Street around 5:50 p.m. Sept. 6 regarding reports of a man -- later identified as Quincy Nunes -- lying on the ground with a stab wound to his upper body, the department reported.

Two detectives were assisted by Criminal Investigations Division personnel, who worked collaboratively to gather evidence, video footage, and statements from witnesses.

Investigators later identified 36-year-old Los Angeles resident Sebastian Emil Gaston as a person of interest. He was taken into custody after police executed an arrest warrant on Nov. 7. Gaston was booked at the Santa Monica police station.

"During his interrogation, Gaston admitted to the murder as well as a previous assault in July. Gaston remains in the custody of the Los Angeles County Sheriff's Department pending trial," the SMPD said in a statement.

Anyone with information regarding the assault was urged to contact SMPD Detective Lawrence Kayondo at [email protected] or Sgt. Alfonso Lozano at [email protected]. The watch commander can be reached 24 hours a day at 310-458-8427.