An activist who led demonstrations against the fatal shooting of unarmed black teenager Michael Brown in Ferguson has been found shot dead in his car.

The body of Darren Seals, 29, from St Louis, was discovered in a burnt-out car in Riverview by police in the early hours of the morning on 6 September.

He was found in after the car fire was extinguished, and was discovered to have been shot. A homicide investigation has been launched but police have not speculated on the motive for the killing, the New York Times reported.

Condolences have poured in for Seals on social media, with many praising his efforts in Ferguson in the wake of Michael Brown's shooting.

Seals co-founded Hands Up United in the wake of the shooting that rocked Ferguson and had been with Michael Brown's mother Lezley McSpadden in Ferguson when a jury opted not to indict the officer who fired the fatal shot, Darren Wilson.

In an interview with MTV following the verdict, Seals said: "And for Mike Brown's mother to be right there in my arms crying — she literally cried in my arms — it was like I felt her soul crying. It's a different type of crying. I've seen people crying, but she was really hurt. And it hurt me. It hurt all of us."

The campaigner added: "It's easy to kill black people because we're the have-nots. We're at the bottom of the totem pole. What people don't understand is, we actually live in a nightmare. We actually live in a place where gunshots [are normal]. We hear gunshots every day."

After they dropped it his mom broke down so bad it hurt my soul #Ferguson #RIP #MikeBrown

A photo posted by Bottom Boyz Management (@kingdseals) on