Simplify the following text for a Grade 7 native English-speaking person.
Original: After Tim quit to form Rise Against , he was replaced in 1999 by Christopher Gutierrez ( known to Fall Out Boy fans as the `` Hey , Chris '' in `` Grenade Jumper '' from Take This to Your Grave ) .
Simplified: After Tim quit to start a new band called Rise Against , he was replaced in 1999 by Christopher Gutierrez .