The teenager told investigators he had been planning the assassination for a year and was convinced he would die in the attempt.
The British national had lived in Hoboken, New Jersey, for around 18 months and had driven to San Bernardino in California before travelling to Las Vegas on Thursday.
The teenager told police he visited the Battlefield Vegas shooting range on Friday where he fired off 20 rounds from a 9mm Glock pistol to learn how to use it.
Sandford also told investigators he had a ticket for a Trump rally in Phoenix, Arizona, for later on Saturday as a back-up.
BMWs are not cheap. Neither is a year on the road. Who is the sponsor?
San Bernardino?
Nice.