So what happened? When the Europeans and Chamorros meet for the first time, blood is spilled. Why?
All our sources for what transpired are European. We have nothing but silence from the Chamorros themselves, who had no means of writing things down. No oral tradition has come down to us, either, from the viewpoint of our ancestors.
Apparently, on the first day when Magellan's flotilla arrived, Chamorros came on board, with the Spaniards' consent, if not encouragement. But when the Chamorros started helping themselves to what they wanted, there was a definite clash of cultures. For whatever reason, the Europeans thought it necessary to use their crossbows - not guns - against the Chamorros. Perhaps it was due to the superior number of Chamorros, or the Europeans' bad physical condition. Remember, they were reduced to sickly, starving men by the time they came to Guam.
At the same time, the Chamorros made off with a skiff from one of the ships. Magellan waited till the next day, when it was light again, to take action.
The Spaniards came ashore, killed seven Chamorros, burnt down many homes and recovered the stolen skiff. Then they sailed away two days later, leaving nothing behind but a name for the islands - Los Ladrones (The Thieves) - which would not be changed till Sanvitores renamed them the Marianas.
Small as it is, for the European sailors, a skiff was worth the trouble of extending their stay, sending in an armed party and taking punitive action against the Chamorros, even taking lives. With a skiff, seamen could test shallow waters first and know for certain where a ship could venture without danger of hitting ground or meeting some other danger.
Re-enactment in Humåtak of the burning of Chamorro homes by Magellan's crew in 1521
So the first deadly encounter between the Europeans and Chamorros was over a ship's goods and a little boat; a skiff. Who owned what. Who could take what.
Blood spills to this very day, even Chamorro against Chamorro, over such things.