Pete Spence (born Elliot Larkin Ferguson; c. 1852–1914) was a small-time criminal known for his association with outlaw Cowboys Frank and Tom McLaury, and Ike and Billy Clanton, of Tombstone, Arizona Territory.

His wife Marietta Duarte testified that Spence and several friends had talked about killing Morgan, but the judge ruled her testimony inadmissible.

Ferguson was wanted for robbery in Goliad Co., Texas in 1878 and left the area for the Arizona Territory near Bisbee and Tombstone where he began using the name of Peter M. Spencer.

[2] On September 8, 1881, a passenger stage on the Sandy Bob line in the Tombstone, Arizona area bound for Bisbee was held up by two masked men.

Marshal Virgil Earp assisted by his brother Wyatt and Sheriff's posse led by Behan attempted to track the Bisbee stage robbers.

Spence and Stilwell were re-arrested on October 13 by Virgil Earp for the Bisbee robbery on a new federal charge of interfering with a mail carrier.

[4] Local newspapers erroneously reported that Spence and Stilwell had been arrested for a different stage robbery that occurred on October 8 near Contention City.

At 10:50 p.m. on Saturday, March 18, 1882, Morgan Earp was shot by assailants who fired through a glass-windowed, locked door at the Campbell & Hatch Billiard Parlor in Tombstone.

[5]: 97  Spence's wife, Marietta Duarte, testified at the coroner's inquest that her husband, Frank Stilwell, Frederick Bode, Florentino "Indian Charlie" Cruz, and a half-breed named Fries[6]: 206 : 176  bragged about shooting Morgan.

After escorting the still recuperating Virgil to the rail road in Tucson, he found Frank Stilwell lying in wait and killed him.

Spence owned a ranch and woodcutting camp at South Pass in the Dragoon Mountains, where he employed Indian Charlie Cruz.