Jeremy Renner has issued his first statement since he was hit by his own snow plow, with authorities revealing that the 6,500kg vehicle had “run over” the star of The Avengers when it began to unexpectedly roll.

On Tuesday afternoon Renner, who remains in a critical condition and is being kept in intensive care, shared a photo of himself in a hospital bed to his Instagram. “Thank you all for your kind words,” the caption read. “Im too messed up now to type. But I send love to you all.”

On Sunday it was revealed that the 51-year-old actor had been airlifted to hospital after being seriously injured while using his snow plow at his home near Reno, Nevada. He underwent surgery for blunt chest trauma and orthopedic injuries, with a witness telling TMZ that one of Renner’s neighbours, a doctor, had put a tourniquet on his heavily bleeding leg until paramedics arrived.

At a press conference on Tuesday, Washoe county’s sheriff, Darin Balaam, said his department’s investigation had found that Renner was struck by the plow while trying to free his car, which was being driven by a family member, from snow near his home.

“Mr Renner went to retrieve his PistenBully or Sno-Cat – an extremely large piece of snow removal equipment weighing at least 14,330 pounds [6,500kg] — in an effort to get his vehicle moving,” Balaam said.

“After successfully towing his vehicle from its stuck location, Mr Renner got out of his PistenBully to speak to his family member. At this point, it was observed that the PistenBully started to roll.

“In an effort to stop the rolling PistenBully, Mr Renner attempts to get in the driver’s seat of the PistenBully. Based on our investigation, it is at this point that Mr Renner is run over by the PistenBully.”

It had been a “tragic accident”, Balaam added, saying the sheriff’s office was investigating a possible mechanical failure in the snow plow.

The northern Nevada region experienced heavy snowstorms over Christmas and new year, with more than 10,000 Washoe county residents losing power.