Updated

Investigators who believe a defendant killed himself in a Phoenix courtroom shortly after a jury found him guilty of arson say their theory is backed up by evidence that includes a canister labeled as cyanide found in his vehicle.

Maricopa County Sheriff Joe Arpaio said Tuesday that the family of Michael Marin, 53, received a delayed email from him the night after his June 28 death in court.

The email includes information about his will in case things went poorly, Arpaio said.

After being convicted of deliberately burning down his $3.5 million Phoenix mansion, Marin collapsed in court and died.

Video from inside the courtroom showed Marin putting his hands over his eyes after the guilty verdict was read and then covering his mouth with both hands.

The email also led Marin's family to his vehicle, and they contacted the sheriff's office.

Investigators found a can labeled "cyanide" in Marin's vehicle. The canister was turned over to the medical examiner's office unopened.

Cari Gerchick, communications director for Maricopa County, said the medical examiner's office could not immediately confirm if the canister indeed contains cyanide.

Gerchick said the medical examiner's office is still determining Marin's cause and manner of death.

Arpaio said investigators have determined that Marin purchased the canister from a California-based Internet site in 2011 using his personal credit card.