Don't ignore the whole other stuff with the failed bombing etc.

From wikipedia:

At 10:10 am,[75] Franz Ferdinand's car approached and Čabrinović threw his bomb. The bomb bounced off the folded back convertible cover into the street.[76] The bomb's timed detonator caused it to explode under the next car, putting that car out of action, leaving a 1-foot-diameter (0.30 m), 6.5-inch-deep (170 mm) crater,[75] and wounding 16–20 people.[77]

Čabrinović swallowed his cyanide pill and jumped into the Miljacka river. Čabrinović's suicide attempt failed, as the old cyanide only induced vomiting, and the Miljacka was only 13 cm deep due to the hot, dry summer.[78] Police dragged Čabrinović out of the river, and he was severely beaten by the crowd before being taken into custody.

Just the mental image of him chucking himself into a river after the failed bombing and then also failing his suicide on two fronts...

Not at all. Things were a powder keg. If it wouldn't have blown at that point, then shortly thereafter.