DETROIT – 
Investigators say four family members robbed and shot someone in an alley on Detroit's west side.
The mother who led her two sons and nephew, in what police call a family affair, are now in jail.
Detroit police officer Allen Williams was off-duty and driving on Detroit's west side.
"I didn't do anything spectacular," said Williams.
When Williams drove near Grand River Avenue and Indiana Street, he says he heard gun shots.
"They sounded very close," said Williams.
Officer Williams went to see what was going on. As he approached an alley, he ran into Tara Sullivan and her boys.
"We saw a guy running into the alley, and right behind them there was a guy with a handgun instead, containing a firearm," said Williams. "I continued to watch the guy who was chasing him along with the group of other people, jump into a car."
Officer Williams followed them.
"I stayed back about maybe a block and a half. I just followed them," said Williams. "I called dispatch and updated them on what I saw, the weapons in the car and the description of the perpetrators."
Within minutes, police caught up with the Sullivan family and pulled them over. As it turned out, Sullivan and sons had robbed a man in the alley, shooting him twice.
"Based on what I saw, I just took the same actions I think any other police officer would do," said Williams.
Police say they also found a bag of guns in the car. Tara Sullivan, her 16-year old-son, whose name was not released, her 21-year-old son Deontay, 23-year old-son Eric and 20-year-old nephew Diontai Manier were all arrested.
Officer Williams is also being praised because police say this family is being linked to other crimes. Police also say the man shot in the alley is in critical condition.