The snippet of security video lasts just under 30 seconds, but it’s enough to capture a 16-year-old boy tumbling to the ground after being shot in the back, then trying to get up after being shot again.

Three hours later, Fred Couch would be dead.

Detectives were reviewing the clip hoping it will lead them to the gunman who approached Couch shortly after 8 p.m. Wednesday at Big Sam’s Mini Mart, 333 W. 119th St. According to updated information, police said he was shot three times, twice in the back and once in the chest.

The video shows the front ends of several vehicles apparently parked in at Big Sam’s. At 8:11 p.m. and 27 seconds people are seen crouched double and running out from behind a white SUV along the driver’s side.

In the video, a figure, apparently Couch, collapses to the ground in front of a green sedan. At 33 seconds, a bald man wearing a blue jacket emerges from the driver’s side of the SUV and extends an arm.

A metal handgun glints in his hand, and a puff of smoke emerges. The figure on the ground flinches.

As the last shot is fired, the SUV backs out of the frame and is gone. At 43 seconds, the figure on the ground turns over and sits up. He then falls back over.

Calumet Area detectives are investigating the shooting and no one was in custody Thursday night, police said.

Couch was a homebody who stayed out of trouble and was often the life of the party, his mother and stepmother said.

“He was beautiful,” his mother Tojuna Williams said. “He kept us all lifted.”

But the 16-year-old’s friends tell a more complex story  —  one that involved neighborhood rivals and frequent minor scrapes with the law.

Couch, a sophomore at Fenger High School, was shot to death at a convenience store around the corner from his house.

“It’s very, very senseless,” Williams said.  “He’s gone. I’m in total shock.”

Muhammad Zain, a Big Sam’s employee, said that a lot of men deal marijuana outside the store on the 300 block of West 119th Street. The dealers have become a nuisance, Zain said.

On Thursday morning, friends and family gathered at Couch’s home on the 11800 block of South Harvard Avenue. Many said they remembered him as a “goofy” teenager who kept the house lively.

He had recently joined the band at Fenger, his mother said, but she didn’t know what instrument he played.

Couch often hosted gatherings in his room, which he meticulously kept clean. He set it up as a sort of lounge, complete with a couch and a speaker system. Hip hop music was constantly playing, his family said.

Couch was big on style. He ironed his jeans every morning and treated his  new gym shoes like trophies, his family said.

“He’s the cleanest son I got,” Williams said, while donning her son’s school ID necklace.

Williams said her son’s father, also named Fred Couch, was shot to death in 1993.

Couch’s father was 23 when he was shot at an Econolodge motel in Calumet City. Police saw three men leaving the motel at 3:15 a.m. and tried to stop them as they sped off toward Chicago on the Dan Ryan Expressway, police said at the time. Police stopped the car near 93rd Street and Stony Island Avenue. The elder Couch was found dead inside.

“It’s really sad, the only son I had with him,” said Williams, before breaking down in tears.

His girlfriend of three years, Shameana Vance, 16, called Couch a “sweetheart.” He would send periodic text messages and often treated her to movies and dinner, she said.

She planned to meet him Wednesday night and worried when he didn’t answer his phone, Vance said.

Couch, however, was often getting into trouble with the law, she said.

He told her that he had recently gotten into a dispute with a group of boys in the neighborhood but didn’t give more details, Vance said. Any criminal record involving Couch isn’t available because he was a juvenile.

Williams said she often had to escort him to court for minor things, but overall Couch stayed out of trouble.

“He was beautiful, he loved people and he was comical,” Williams said. “He can do wrong, but he’s mainly doing right.”

His stepmother, Debra Jones, said she had a conversation with him recently about getting his life together and getting a job.

“He told me he had started to see things in a more positive light,” Jones said. “He was too young to die like that.”

Many in the neighborhood said Couch was a familiar face on the block. Shawn Fleming, 31, whose cousin was a close friend of Couch’s, said Couch got himself into minor run-ins with the law  but he did nothing severe enough to get himself killed.

“He’s too young to die like that,” Fleming said. “He’s just a schoolboy.”