A former MMA fighter turned anti-gun advocate has been arrested after allegedly shooting and killing a man at a pool party in Colorado. 

Lumumba Sayers, 46, was taken into custody on Saturday after police say he murdered 28-year-old Malcolm Weston during a children’s birthday party in Commerce City. 

Sayers son, Lumumba Sayers Jr, was shot and killed last August in Denver with an arrest affidavit seen by News 9 suggesting his actions were retaliation for his son. 

According to the affidavit, witnesses saw Sayers Sr. ‘walk up and shoot the victim in the head at close range’.  

The document continued: ‘Witnesses had stated the [shooter’s son had been murdered about a year ago by a friend of the deceased and this murder was probably in retaliation or revenge.’

Lumumba Sayers, 46, was taken into custody on Saturday after police say he murdered 28-year-old Malcolm Weston

Sayers prepares to enter the cage before his bout with Derek Brunson at the Strikeforce event at Sears Centre Arena on July 30, 2011 in Hoffman Estates, Illinois

The outlet also spoke to Watson’s sister who said the birthday party had been for his own 5-year-old son. 

She also protested her brother’s innocence and claimed he had nothing to do with the death of Sayers son. 

She said: ‘How is it a revenge killing if my brother isn’t the one who had anything to do with it?.’

His sister also described Watson as a man who wanted to be a great father and care for his family, calling him a loving brother. 

His sister described Watson as someone who wanted to be a great father and be around his family and make sure his sisters were all fine. She called him a loving little brother.