A woman who lost her two young grandsons in the 1995 Oklahoma City bombing says the official account of a lone bomber is false — a direct challenge to the FBI's version of America's deadliest domestic attack.

• Kathy Sanders, who lost grandsons aged two and three, has spent 30 years digging into the case and says many more people were involved than the government admits.
• She points to warnings before the blast: an ATF informant reported plans to bomb Oklahoma City buildings months earlier, and the federal courthouse and fire department were told to watch for terrorist activity.
• Witnesses reported a bomb squad truck downtown the morning of the attack, though the fire chief denied it.
• Dozens of witnesses placed Timothy McVeigh with a second man, but the search for "John Doe No. 2" was dropped and none of those witnesses were called at trial.
• A German national linked to the same religious compound as the informant was never interviewed in person and was allowed to leave the country.

Outlook: Sanders is pushing for a federal grand jury, and renewed attention to the case is likely to keep pressure on the FBI to explain what it knew.