NYPD detectives have charged the Queens man accused of stabbing his mother-in-law to death and torching the family home before trying to take his own life, police said Saturday.

Wei Sheng Chen, 27, is facing multiple counts of murder, attempted murder, arson, assault and weapons possession for the Thursday afternoon rampage inside the family’s Smart St. home in Flushing.

Chen’s wife was outside the home and screaming for help as the suspect knifed his spouse’s mother, Qiujin Shi, and his 17-year-old brother-in-law, then lit a mattress on fire in a back bedroom around 3:30 p.m., cops said.

As the fire began to spread, Chen then slit one of his wrists in a suicide attempt, according to police.

Neighbors heard Chen’s wife yelling for help and called 911. Responding cops and firefighters

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