Short answers, pulled from the story.
The Soviet Union occupied the Baltic states in the summer of 1940. Lithuania was invaded on the 15th of June 1940, followed by Estonia and Latvia on the 16th of June, after Moscow issued ultimatums to all three countries.
The Soviet government feared Germany would use the Baltic states as a corridor to reach Leningrad. The Molotov-Ribbentrop Pact had already given the Soviets formal freedom of action over the three countries, and after stationing troops there in 1939, Moscow moved to full annexation in 1940.
According to a Time magazine article published during the invasions, around 500,000 Soviet Red Army troops occupied the three Baltic states in a matter of days. The forces allocated for possible military action numbered 435,000 troops, supported by around 8,000 guns and mortars, over 3,000 tanks, and over 500 armoured cars.
No. The elections held on the 14th and the 15th of July 1940 were rigged after illegal amendments to electoral laws ensured only Communists and their allies could run. The results were entirely fabricated: the Soviet press service released them before the polls closed, and the tallies had already appeared in a London newspaper a full 24 hours before voting ended.
American Foreign Service employee Henry W. Antheil Jr. was killed when two Soviet bombers shot down the Finnish passenger plane Kaleva on the 14th of June 1940. The plane was flying from Tallinn to Helsinki and was carrying three diplomatic pouches from U.S. legations in Tallinn, Riga, and Helsinki.
The presidents of Estonia and Latvia were imprisoned by Soviet authorities after being forced to resign and later died in Siberia.