We compare results of the solar high-energy proton detection with the neutron monitor network in Ground Level Enhancement (GLE) events and the data of pion-decay gamma-ray emission produced by high-energy protons interacting at the Sun. Observational data support the idea of a common origin of the GLE-producing protons and the protons interacting at the Sun to produce sustained gamma-ray emission. Then we discuss capabilities of the CME bow-shock acceleration models to explain the observational data and argue for the flare and CME synergy in production of high-energy protons in the long duration events.