Ann Eliza Young says the Parrish brothers were killed for apostasy.

Date: 1876
Type: Book
Source: Ann Eliza Young
Excommunicated
Critic
Hearsay: Unsourced
Late
Reference: Ann Eliza Young, Wife no. 19, or, The story of a life in bondage : being a complete exposé of Mormonism, and revealing the sorrows, sacrifices and sufferings of women in polygamy (Hartford, CT: Dustin, Gilman, & Co. 1876), 197
Scribe/Publisher: Dustin, Gilman & Co.
People: Beason Parrish, William Parrish, Ann Eliza Young, Duff Potter
Audience: Reading Public
Transcription: The Potter and Parish murders at Springville, and the assassination of Dr. Robinson at Salt Lake, are notorious. The Parrish brothers were murdered for apostasy, Dr. Robinson because he was a Gentile whose influence was extending in the Territory, so popular was he, and consequently the authorities considered him dangerous.
Source Link: https://archive.org/details/wifeno19orstoryo00youn/page/196/mode/2up
Citations in Mormonr Qnas: Blood Atonement and Capital Punishment