The fall of the Bastille occurred on July 14, 1789. At this time, Thomas Jefferson was still in Paris as minister to France. He was at the Hôtel de Corny on the evening of the 14th, and later wrote about that night in a letter to John Jay on July 19, 1789 and in his Autobiography. Jefferson visited the prison twice after the event.
Primary Source References
1789 July 17. "Pd. expences to Bastille 2 [livre tournois]."
1789 July 19. (Jefferson to John Jay). "The demolition of the Bastille is going on...we cannot find with certainty that any body has been killed but the three beforementioned, and those who fell in the assault or defence of the Bastille. How many of the garrison were killed no body pretends to have everheard. Of the assailants accounts vary from 6. to 600." 
1789 July 20. "Pd. seeing Bastille 6 [livre tournois]. --renewed sbscrptn. Point du jour 6 [livre tournois]."
1789 August 21. "Gave for widows of those who were killed in taking the Bastille 6 [livre tournois]."
1821 January 6. (Autobiography). "They found a great collection of people already before the place [Bastille], and they immediately planted a flag of truce, which was answered by a like flag hoisted on the Parapet. The deputation prevailed on the people to fall back a little, advanced themselves to make their demand of the Governor, and in that instant a discharge from the Bastile killed four persons, of those nearest to the deputies. The deputies retired. I happened to be at the house of M. de Corny when he returned to it, and received from him a narrative of these transactions. On the retirement of the deputies, the people rushed forward & almost in an instant were in possession of a fortification defended by 100. men, of infinite strength, which in other times had stood several regular sieges, and had never been taken. How they forced their entrance has never been explained. They took all the arms, discharged the prisoners, and such of the garrison as were not killed in the first moment of fury; carried the Governor and Lt. Governor to the Place de Greve...cut off their heads, and sent them thro' the city in triumph to the Palais royal."