HOUSTON – New surveillance video shows the moment fireworks inside a vehicle exploded when a man shot at it following a road rage incident.

The incident was reported about 10 p.m. in the 1800 block of West Mount Houston Road near Ella Boulevard, and it left a family of four suffering from severe burns, police said.

Witness Peter King said the situation started when a man and his family were buying fireworks and got into an argument with another man who parked behind the man's truck, blocking the family in.

"I just looked up to see what was going on," said Daniel Rocha, the manager of a firework stand at the corner of 249/Veterans Memorial. "He was like, 'Who does this car to belong to?' He seemed like he was really mad."

King says the argument ended and the father went back to his truck.

"He jumped in the truck and took off (but) the other guy wouldn’t let it go and came behind him," said King.

The man followed the father about 200 yards and pulled into a nearby gas station, King said.

The man pulled out a gun, so the father went back to his vehicle where his wife, his 1-year-old and his 2-year-old were waiting and tried to drive away, deputies said.

WATCH: Surveillance video of road rage shooting that ignited fireworks in truck

When the man started to pull away, the other man fired a shot into the family’s vehicle, striking some fireworks and causing them to ignite, authorities said.

"When he jumped in his truck to leave the other man started shooting at him," said King. "(The explosion) sounded like a cannon. Everybody started running and getting out the way. It was a horrible feeling to see something like that."

The car went up in flames, trapping the family inside, but good Samaritans who saw the blaze were able to get the family out, deputies said.

According to authorities, all four of them suffered severe burns.

“The two children were (taken via Life Flight) to UTMB Galveston with severe burns,” said Harris County Sheriff’s Office Violent Crimes Detective Tom Turner. “The mother was also transported (and) the father has since been transported.”

Authorities said the gunman is believed to be in his 20s. Deputies believe he is driving a newer model light-colored Ford Explorer and there were three other people inside his vehicle, including a woman.