Four people were wounded, one of them critically, at a house party just after midnight Sunday in Baldwin Park.
The shootings were at about 12:30 a.m. in the 3700 block of Loma Lane, said Baldwin Park police Sgt. Raymond Findley.
Three of the victims had non-life threatening injuries and the fourth victim was critically wounded, Findley said.
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"It appears the shooting occurred as a result of a confrontation of two groups of party goers," he said.
It was unknown if the shooting was gang-related.