Short answers, pulled from the story.
Albert Sidney Johnston graduated from the United States Military Academy at West Point in 1826. He finished eighth out of forty-one cadets in his class and received a commission as a brevet second lieutenant in the 2nd U.S. Infantry.
Albert Sidney Johnston fought a duel with Texas Brigadier General Felix Huston because Huston felt offended by Johnston's promotion to senior brigadier general in command of the Texas Army. Johnston explained years later that he fought Huston as a public duty because the safety of the republic depended on the efficiency of the army.
Albert Sidney Johnston died from blood loss within minutes after taking a bullet behind his right knee which clipped part of his popliteal artery. No medical personnel were present because Johnston had sent his personal surgeon to treat wounded Confederate troops earlier.
On the 21st of August 2017, Albert Sidney Johnston's statue was taken down as part of a wave of Confederate monument removals. Plans were announced to add it to the Briscoe Center for American History.
The War Department accepted Albert Sidney Johnston's resignation from the United States Army on the 6th of May 1861. He traveled across the southwestern deserts to Texas and crossed the Colorado River into Confederate territory on the 4th of July 1861.