He was recorded in the 1850 census as Jonathan M. Foster age 11, but all later records refer to him as simply Milton, so I am flipping the order of his given names.

From an article in the Ashland Independent.

10 Nov 1881, page 2 - Intense excitement reigned in Grayson on Wednesday of the 2nd instance because of a bloody shooting between Steve Stamper, Milton Foster and Bruce Alfrey, all Rowan County citizens. A dispute arose over the correctness of statements made under oath in a trial of moonshiners before U.S. Commissioner Bowling. Alfrey called Stamper a liar; Stamper drew a revolver and fired on Alfrey, shooting him in the hand. Foster started to run, Stamper shot him, the ball taking effect between the elbow and shoulder in the muscles of Foster’s left arm. Stamper started to run. Foster and Alfrey fired on him at the same time. Foster missed, but the ball from Alfrey’s .32 caliber revolver struck Stamper between his tenth and eleventh rib, passing through his body and out below the lower end of his breast bone. Stamper is recovering in the Grayson Hotel. Dr. Louis Prichard is in attendance. Foster was before the court for illicit distilling.

A week later there is an addendum:

17 Nov 1881, page 2 - Bruce Alfrey was tried in Grayson last Thursday. All charges against him were dismissed because of insufficient proof. Stamper has recovered from his wounds.

From censuses, this would be Stephen Stamper, born about 1845 in Letcher Co., son of Isaac Daniel Stamper and Mary “Polly” Adams. He married Elizabeth Merrill. In the 1880 census, they were living in Blairs Mills, Morgan Co., Ky. (Contrary to the article, there was no Stephen Stamper living in Rowan Co. But the altercation took place in Carter Co.) Stephen Stamper died 5 April 1882 in Morgan Co. at age 37, five months after he was shot by Bruce Alfrey. I do not know his cause of death.

She went by her middle name Ellen.

1870 census of Rowan Co., Kentucky, Pearce prec., taken 15 June, lists on p. 3/123, family #16 (next door to Ellen's parents, James & Lucinda Jones):
Foster, Milton, 31; Ellen, 25; Mary, 8; Sally, 6; Lucinda, 4; William, 2/12, b. April. All born in Kentucky.

1880 census of Rowan Co., Kentucky, Pearce precinct, lists as family #200 (next door to Ellen's brother, William & Barbara Jones):
Foster, Milton, 40; Ellen, 35; Sarah A., 15; Annie, 11; James, 10; Robert, 8; John, 4; Jessee, 3/12. All born in Kentucky.

James is the same son listed as William age 2 months in 1870. Annie is probably the same daughter listed as Lucinda in 1870, since she is recorded here as older than James.