An off-duty St. Louis county police officer shot and killed a man on Saturday after an argument about Black Lives Matter on Facebook led the suspect to break into the officer’s home.

Police identified the intruder as 20-year-old Tyler Gebhard.

Gebhard, according to the St. Louis Post-Dispatch, threw a concrete planter through the officer’s window after the cop’s wife refused to let him into the home.

Police said Gebhard had recently made threats toward the officer’s family on Facebook.

Gebhard’s uncle, Patrick Brogan, said the officer and his nephew first became acquainted through a church connection but became estranged after arguing on Facebook about Black Lives Matter.

The off-duty St. Louis county police officer has not been identified, but St. Louis County Police Chief Jon Belmar did acknowledge Saturday during a press conference that the officer was a three-year veteran of the department.

Gebhard was a former high school football star and a vocal supporter of Black Lives Matter, Brogan told the newspaper.

“He had a lot of mental problems the last few months,” Brogan said, adding that his nephew suffered from bi-polar disorder and was known to forget to take his medication; he had “A lot of difficulties in life.”

Gebhard’s family said the argument between the officer and him led the 20-year-old to travel from Affton, MO, to Lakeshore, MO, about a mile drive, late Saturday afternoon.

“He walked over there and into a gunfight,” Brogan said. “When he got there he was met with a gun and the guy killed him.”

“He was like a normal 20-year-old, (the family) had to stay on him to take his medication,” Brogan said of his nephew.

Belmar gave a detailed account of the incident.

Belmar said Gebhard rang the officer’s doorbell at 5:50 p.m., noting that the cop’s wife recognized Gebhard. She closed the door and ran to the back of the house with her mother-in-law, a toddler, and an infant.

Gebhard had already thrown a 50-pound concrete planter through a window to enter the home before the officer could reach the front door.

The officer yelled “get down, get down, get down,” Belmar said, according to family members who were in the house.

Moments later, they heard several shots fired, Belmar said.

Gebhard was shot twice in the chest, and was pronounced dead after being rushed to St. Anthony’s Hospital.

“I don’t think the officer had a choice — I honestly don’t,” Belmar said.

The incident in St. Louis county occurred just days after Houston New Black Panther Party member Micah X. Johnson ambushed and opened fire on Texas law enforcement officers, murdering five and wounding seven others.

Gebhard’s personal Facebook page was rife with condolences from friends and former teammates who expressed shock at his passing, some of them recounting that they’d just spoken with their friend hours before his death.

“We are sick for both families because it was senseless,” Brogan said. “It was a senseless death.”

The officer was placed on administrative leave pending investigation of the incident.

Follow Jerome Hudson on Twitter @jeromeehudson.