This is not being done by ERCOT that manages power distribution in Texas. Your friend had a local power failure, probably caused by a downed power line.

Rolling blackouts would be documented here if they were happening: https://www.ercot.com/services/comm/mkt_notices/opsmessages

More info: https://www.kxan.com/news/texas/do-you-know-the-difference-b...