Date: 201807
Local time of day: 0601-1200
Location: SAT.Airport, TX
Flight conditions: VMC
Light: Daylight
Aircraft: Medium Large Transport
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Final Approach
Airspace: Class C SAT
ATC / advisory: TRACON SAT
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Human factors: Communication Breakdown
Second reporter function: First Officer; Pilot Not Flying
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT
Detector: Person Air Traffic Control; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Contributing factors: Environment - Non Weather Related; Airport; Human Factors
Primary problem: Human Factors

Narrative: We had a caution EGPWS (Enhanced Ground Proximity Warning System) event in KSAT in visual conditions. I am not 100% sure exactly what happened but there was some definite miscommunication on flight deck. We were being vectored on a base to 13R and cleared for visual. We were at 3000 ft and auto pilot on and approach mode was armed. FO (First Officer) vectored himself via heading bug to approximately a 45 degree intercept of extended runway centerline. It was briefed and appeared to be being flown correctly. I had called LOC and glideslope alive call. I noticed a tower at 11-12 o'clock position and was pretty tall. I was pointing out tower to FO when I noticed that 2000 ft was set in altitude alerter. I queried why and noticed we had joined localizer still on autopilot but we were now descending. I was explaining to FO to arrest his rate of descent and if he was visual with tower. About the same time we got the 'caution obstacle' and our terrain maps pulled up and I told him to level. He climbed back up a few hundred feet or so and the aircraft captured the glideslope. About this time ATC called and told us 'low altitude alert' to check altitude. I told him we had corrected and were visual and on glideslope. I am confused because at some point when approaching final approach fix the FO said he thought I was telling him he was high and to get down while I was pointing out tower. I think he misunderstood my tower point out and just assumed he was high. I am not trying to 'hand my fellow pilot out to dry' but cannot not make heads or tails of what happened. On approaches I make inside and outside scans every couple seconds and a lot happened in that time. He did say he set lower altitude to get down but not sure why. He didn't verify altitude set with me and I happened to be heads out staying visual with tower. I think the close proximity to tower and the misconception of being high he descended to fast to quick and we got the EGPWS caution. We got down to about 2500 feet and with the descent rate I assume we were on a path to hit tower unless we intervened. The tower height is 1608 ft tall. We landed without further incident.


Second narrative: [Report narrative contained no additional information.]


Synopsis: Air carrier flight crew reported activating the terrain warning system due to descending early on approach.