Authorities are investigating whether Las Vegas shooter Stephen Paddock may have planned additional shootings and possibly even a car bombing.

Sources say that Paddock booked hotel rooms in Chicago during the Lollapalooza music festival during the first week of August, ABC News reported Thursday.

NBC News notes that although Paddock booked the room in Chicago, he never checked in, and there was no indication that he even traveled to the city.

Paddock also reportedly searched online for hotels near Boston’s Fenway Park, although he may have decided against targeting the Major League Baseball park because most of the hotels in the area have an obstructed view of Fenway, which would not have allowed him to target fans the same way he did in Las Vegas.

Another disturbing detail that emerged from the new round of reports on Thursday was that Paddock might have planned a car bombing.

“A federal official said authorities are looking into the possibility Paddock planned additional attacks, including a car bombing,” ABC News reports. “The official wasn't authorized to discuss the matter publicly and spoke on condition of anonymity.”

Clark County Sheriff Joseph Lombardo confirmed earlier this week that they found ammonium nitrate in Paddock's car – the same chemical compound used in the Oklahoma City bombing that killed 168 people in 1995. Officials also reportedly found a significant quantity of explosives inside one of his residences.