An unarmed black man killed by a white Oklahoma officer who was responding to a stalled vehicle can be seen in police video walking away from officers and toward his SUV with his hands up before he approaches the driver's side door, where he drops to the ground after being shocked with a stun gun then fatally shot.

In Tulsa police helicopter footage that was among several clips released on Monday showing the shooting of 40-year-old Terence Crutcher and its aftermath, a man in the helicopter that arrives above the scene as Crutcher walks to the vehicle can be heard saying "time for a Taser". He then says: "That looks like a bad dude, too. Probably on something."

Police Chief Chuck Jordan announced before the video's release that Crutcher had no weapon on him or in his SUV when he was shot on Friday. It's not clear from the footage what led Betty Shelby, the officer who fired the fatal shot, to draw her gun or what orders officers might have given Crutcher. Local and federal investigations are under way to determine whether criminal charges are warranted in the shooting or if Crutcher's civil rights were violated.

Family calls for charges

Crutcher's twin sister, Tiffany Crutcher, called for charges on Monday.

"The big bad dude was my twin brother. That big bad dude was a father," she said. "That big bad dude was a son. That big bad dude was enrolled at Tulsa Community College, just wanting to make us proud."

Police video shows Crutcher walking toward his SUV that is stopped in the middle of the road. His hands are up and a female officer is following him. As Crutcher approaches the driver's side of the SUV, three male officers walk up and Crutcher appears to lower his hands and place them on the vehicle. The officers surround him, making it harder to see his actions from the dashboard camera's angle.

Crutcher can be seen dropping to the ground. Someone on the police radio says, "I think he may have just been tasered". One of the officers near Crutcher backs up slightly.

Then almost immediately, someone can be heard yelling, "Shots fired!" Crutcher's head then drops, leaving him completely lying out in the street.

After that, someone on the police radio can be heard saying, "Shots fired. We have one suspect down."