The letter says: "Our pastor, Emerson Wiles, will be at St. John's this Sunday morning at 8:30 to lead that worship service.He will be back in time to preach at First Baptist for the 8:30 service here." 

No, Emerson is not able to be in two places at one time, as this confusing wording may indicate. The service at St. John's, more of a chapel-style service, traditionally lasts around 30 minutes. Emerson will preach that service and drive to First Baptist to be in place to begin preaching at 9 AM - following the music, offertory, choir special, etc. that typically happen at the beginning of our 8:30 AM Traditional Service.