Osvaldo Rivera was arrested Sunday afternoon and charged with murder and attempted murder after allegedly stabbing a 6-year-old boy and his 12-year-old sister earlier Sunday, WPVI-TV, Philadelphia, reported.
Prosecutors said Rivera, who goes by the nickname "Popeye," was known to stay at an apartment near where the children lived. When investigators found him there, he was hiding between a mattress and a bedroom wall, the report said.
Investigators said they also found blood-stained sneakers that matched bloody footprints found at the crime scene.
While being questioned by investigators, Rivera allegedly admitted to smoking "wet," a combination of marijuana and PCP, before the incident, police said.
Police found the children, Dominick and Amber Andujor, in their home with their throats slashed around 2 a.m., the Philadelphia Inquirer reported.
Dominick died, while Amber was listed in critical condition, authorities said. Two other girls, 14 and 9, were in the home at the time but were not injured.
The children's mother was in the hospital recovering from surgery at the time of the incident, WPVI-TV said.