The fatal incident happened along TX 137, about 11 miles north of Lamesa on January 17th.
According to The Lamesa Press-Reporter, Mariano Mojica Jr. was trying to close a valve in the cellar of a pumpjack when the H2S gas (hydrogen sulfide) overcame him.
The Lamesa man was working with a three-man crew that was employed by Hatchett Roustabout of Lamesa when the incident occurred.
Mojica, 57, was pronounced dead at the scene by Dawson County Justice of the Peace Denise Dyess at 7 PM on January 17th.
Dyess ordered that Mojica's body be sent for an autopsy.