PITTSBURG, Calif.—Pittsburg police say four people have been arrested in connection with the stabbing death of a man who allegedly was their co-conspirator in a plot designed to scare a man into moving out of the apartment he shared with his estranged wife.

Lt. Ron Raman said the wife, 28-year-old Charmaine Taijeron, and her 22-year-old boyfriend, Matt Parker, were among the quartet who remained jailed Wednesday on suspicion of murder, even though it was Taijeron's husband who stabbed 49-year-old Robert Lindsey to death.

Raman says Lindsey and two other men broke into the apartment Tuesday morning intending to pose as burglars as part of the plot devised by Taijeron and Parker. Lindsey and the husband ended up in a struggle, leading to Lindsey's death.

The husband was not arrested because authorities believe he acted in self-defense.