[8] In Mississippi, he was among 140 demonstrators arrested in Natchez on October 2, 1965, and detained three days at Parchman State Prison Farm, where he and others were kept naked in cold cells with no bedding.

[14] In Holmes County, he helped organize a Head Start program and a voter registration drive that registered over 6,000 African Americans for the 1967 election.

[15] Together with his father, Shimkin organized a project through which 18 African American students from Holmes County were selected to attend the University of Illinois.

Returning to his studies, Shimkin graduated with "high distinction" in government from Indiana University Bloomington in 1969,[18] then became a community development worker with International Voluntary Services (IVS) in Laos[19] and South Vietnam.

[26] Shimkin and his boss, Newsweek's Saigon bureau chief Kevin P. Buckley, produced a 4,700-word story that specifically alleged "that thousands of Vietnamese civilians have been killed deliberately by U.S.

"[28] Pared back to 1,800 words by Newsweek editors who feared that the allegations would be seen as a "gratuitous attack" on the administration of President Richard M. Nixon following the revelations of the My Lai Massacre,[29] the story was published in the June 19, 1972, issue under the title "Pacification's Deadly Price", but it attracted little attention.

On June 8, 1972, a month before he died, Shimkin was one of the journalists present at Trảng Bàng in Tây Ninh Province when photographer Nick Ut captured his famous image of the nine-year-old Vietnamese girl Phan Thị Kim Phúc and some other children fleeing a napalm attack.

Two South Vietnamese Skyraider aircraft went off course and dropped the incendiary bombs near the journalists, resulting in the deaths of two children and inflicting serious burns on others, including Kim Phúc.

"[33][34] While covering fighting north of Saigon on National Route 13 (the highway to An Lộc) during the first week of July 1972, Shimkin went to the aid of a wounded South Vietnamese soldier and carried him to safety under heavy mortar fire.

[36] On July 12, 1972, Shimkin and another reporter, Charles "Chad" Huntley, became lost in Quảng Trị Province while covering Allied[37] operations to expel North Vietnamese forces that had occupied the area in the Easter Offensive.

An explosion occurred, he started to crumple...."[40] A veteran of the U.S. Special Forces, Huntley was only slightly wounded and attributed his survival and escape to his military training.

"[6] According to information from Shimkin's IVS application, he liked the novels of William Faulkner and Theodore Dreiser as well as reading political science and American history.

[47] At the time of his death he had been accepted for graduate study at Princeton University and hoped to write the "definitive history" of the Vietnam War.