He visited Vanderbilt of the SEC last week, nearly two months after his official campus visit to BYU.
Rivals.com and Scout.com both have Gunter listed as a three-star recruit.
Gunter's commitment brings BYU's total to 21 and comes on the heels of a commitment from Bingham High defensive end Langi Tuifua over the weekend.
The Cougars are still in the running for several high-profile recruits, including Bingham five-star defensive tackle Jay Tufele, Iowa City (Iowa) four-star receiver Oliver Martin and Westlake four-star safety/receiver Chaz Ah You.
Sitake did receive some bad news this week as well. Tight end Cameron Latu, a member of the 2018 signing class (this year's juniors) from Salt Lake City's Olympus High noted on Twitter that he has decommitted from BYU.
Here's the updated list of BYU's 21 commits:
BYU's 2017 Commits (21)
Jackson McChesney, 6-0, 170 RB from Highland, Utah (Lone Peak High School)
Isaac Rex, 6-4, 225 TE from San Clemente, Calif. (San Clemente High School)
Tanner Baker, 6-5, 225 DE from Acworth, Georgia (Allatoona High School)
Preston Lewis, 6-2, 225 DE from Highland, Utah (Lone Peak High School)
Ammon Hannemann, 6-2, 190 safety from Highland, Utah (Lone Peak High School)