Father Michael J. McKeirnan was a Maryknoll missionary. His surname is often misspelt as "McKiernan". He was ordained on 22 June 1941 and assigned to Wuchow (Wuzhou), China. Father McKeirnan and his group of newly ordained priests had arrived in Hong Kong just before the Japanese invasion and became trapped in the city and not able to proceed to their inland missions. (Father McKeirnan mentioned in a field trip made to Maryknoll House on 8 December 1984, that he had arrived in Hong Kong on a "Pan Am Flying Clipper" the night before Pearl Harbour was attacked).
After the fall of Hong Kong, he was interned with other Maryknoll priests at Stanley Camp until September 1942 (see here). Upon release and having gained permission from the Japanese authorities to enter China, he and a group of fellow priests left Hong Kong and arrived safely in Kweilin (Guilin) at the end of January 1943.
Father McKeirnan later made his way to Wuchow. The mission at Wuchow was completely destroyed by Japanese bombing in September 1943, but luckily Father McKeirnan was not injured. He would later be evacuated and served as chaplain with the U.S. Air Force. He remained in China until 1949.
After a period of time in the United States, Father McKeirnan returned to Hong Kong in 1956. He served in high-level posts such as Regional Vicar, Director of Maryknoll's Stanley House and Director of the Bishop Ford Centre in Kowloon. Father McKeirnan left Hong Kong in January 2005.
Source
1. Maryknoll Mission Archives: https://maryknollmissionarchives.org/deceased-fathers-bro/father-michael-j-mckeirnan-mm/
2. Surname verification: https://www.myheritage.com/research/record-10002-82862403/michael-j-mckeirnan-in-us-social-security-death-index-ssdi
3. Catholic News Service - Newsfeeds dated 23 June 1941. See here
4. Brooklyn Daily Eagle dated 5 February 1943. See here
5. The St. Louis Review dated 17 September 1943. See here
6, RAS Field Trip to Maryknoll House on 8 December 1984. See https://hkjo.lib.hku.hk/archive/files/c6fddd943c0a7783a7c68dbdb1c05e20.pdf