COVINA -- A 28-year old man is in custody today for allegedly stabbing his 2-year-old son to death after arguing with the toddler's mother, police said.

Alex Trujillo, of Covina, was treated for self-inflicted stab wounds before being booked on suspicion of murder, Covina police Lt. John Curley said.

Officers were sent to a home in the 100 block of South Waterbury Avenue, where Trujillo lives with his mother, about 9:15 p.m. Tuesday on a report that he was acting in a "bizarre and strange" manner, Curley said. He was outside when they arrived, but ran back into the residence.

Police surrounded the home, and an officer saw Trujillo inside stabbing himself, prompting officers to kick open the door to intervene, Curley said. Trujillo fought with the officers, who noticed the injured toddler after restraining his father.

The child was rushed to County-USC Medical Center, where he died as surgeons tried to repair his injuries.

Sgt. Dave Foster said Trujillo had been arguing with his girlfriend, and his brother called 911 when the suspect armed himself with a kitchen knife.

The girlfriend, who did not live at the house, was outside with Trujillo's brother when her son was stabbed, police said.

Police said other family members had barricaded themselves in another part of the house, and may not have known what was happening to the toddler.

"Last night, it had come to a head to the point where she (the girlfriend) couldn't manage him or sustain her relationship with what was happening with him, and they began to fight about the relationship -- whether the relationship was going to continue or not," Foster said.