A man killed in the explosion of a car sent letters to the police and his family

One of three people killed during Saturday's deadly car bomb explosion in Allentown had sent letters the same day to the Allentown Police Department and family members.

But what he's writing is unknown at the moment, reports WFMZ, to whom the letters were transmitted by a source.

The Bureau of Alcohol, Tobacco, Firearms and Explosives is expected to release the findings of its blast investigation at a news conference today at 11:30 am

According to reports, Jacob Schmoyer, one of three victims of the explosion, sent letters dated Saturday. His 2-year-old son, J.J., and a friend, David Hallman, were also killed in the blast. All three were inside the car.

Investigators spent days discovering the origin of the explosion in the 700 block of Turner Street, which destroyed nearby property and smashed windows.

According to The Morning Call, a security video shows Hallman, 66, getting into the car with Schmoyer and his son. About two seconds after Hallman closed the door, the car exploded.

Lehigh County General Counsel Jim Martin calls it a criminal investigation and says the person in charge was probably in the car at the time of the blast, reports WFMZ.